Deliverability skill

Warm-up metrics reader

A high warm-up score measures a cooperative network, not cold inbox placement. Share your warm-up stats and the assistant tells you which mailboxes are ready, which to investigate and what to test.

Works with

One Markdown file, free to use and change. It reads only what you paste into the chat.

What it does

What the skill checks

  • Explains why warm-up scores overstate cold email placement
  • Reads the initial spam share, the warm-up number that stays honest
  • Splits results by recipient provider: Google, Gmail, Microsoft, Outlook.com
  • Flags rising spam share, one weak provider and domain-wide drops
  • Checks warm-up age: at least 2 weeks before cold sending
  • Recommends a seed test with a neutral control when placement is unknown

Use it when

  • Deciding whether new mailboxes are ready to send cold email
  • Warm-up health looks fine but reply rates dropped
  • Comparing mailboxes or domains to pick which ones to send from

Example

What you paste and what you get back

You
12 mailboxes on 3 domains, 21 days of warm-up, all 97-99% health. One domain shows 18% saved from spam on Gmail, the others under 3%. Can we start cold?
Assistant, with the skill
example-mail.com: 21 days, 98% health, 2% Gmail spam share. Ready, ramp slowly.
example-team.com: 21 days, 97% health, 18% Gmail spam share. Investigate.
Red flag: health looks fine because peers rescue emails from spam. The 18% initial spam share is the real signal.
Next: check SPF, DKIM and DMARC on example-team.com, keep it off cold sending, run a seed test with a neutral control message.

Install

Install it in your assistant

The same file works everywhere. Claude and Claude Code load it as a skill; the other assistants follow it as instructions.

Claude Code

  1. Run the command below. It saves the skill to your personal skills folder, available in every project. For one project only, use .claude/skills in the project instead.
  2. Start a new Claude Code session. Claude uses the skill when your request matches its description, or when you name it.
Terminal
mkdir -p ~/.claude/skills/warmup-metrics-reader
curl -fsSL https://outreach2day.com/skills/warmup-metrics-reader/SKILL.md -o ~/.claude/skills/warmup-metrics-reader/SKILL.md

Claude (web and desktop)

  1. Download the ZIP file.
  2. In Claude, open Settings, find Skills under Capabilities and upload the ZIP. Skills need code execution to be turned on for your account.
  3. Ask for the task in any chat. Claude loads the skill when the request matches.

ChatGPT

  1. Download SKILL.md.
  2. Paste its text into a Project's instructions or a custom GPT's instructions. For a single chat, attach the file and write: follow the instructions in this file.

Gemini

  1. Download SKILL.md.
  2. Create a Gem and paste the file's text into its instructions, or attach the file to a chat and ask Gemini to follow it.

Grok

  1. Download SKILL.md.
  2. Paste its text into a Project's instructions, or attach the file to a chat and ask Grok to follow it.

Cursor and other coding agents

  1. Save the file as a project rule with the command below. Cursor reads the description to decide when to apply it.
  2. Agents that read AGENTS.md (Codex and others): paste the text into AGENTS.md or reference the file from it.
Terminal, in your project
mkdir -p .cursor/rules
curl -fsSL https://outreach2day.com/skills/warmup-metrics-reader/SKILL.md -o .cursor/rules/warmup-metrics-reader.mdc

Source

The full SKILL.md

Read it before you install it. Change the rules to match your own setup.

warmup-metrics-reader/SKILL.md
---
name: warmup-metrics-reader
description: Reads email warm-up dashboards and tells the user what the numbers do and do not say about cold email placement. Explains why a 95-100% warm-up score is not proof that cold emails reach the inbox, which warm-up numbers are still honest (the share that first landed in spam, per recipient provider), what red flags to act on, and when to run a seed placement test instead. Use when the user shares warm-up scores, warm-up health, per-provider warm-up stats or screenshots from a warm-up tool, or asks whether mailboxes are ready to send cold email.
---

# Warm-up metrics reader

You read warm-up statistics and translate them into decisions: keep warming, start sending, investigate, or run a placement test. You never tell a user that a high warm-up score means their cold emails land in the inbox.

## Why warm-up scores overstate placement

Warm-up tools send emails between mailboxes in a cooperative network. The receiving peers open the messages, reply, mark them important and move them out of spam. That behaviour is the point of warm-up, but it also means the headline score measures a friendly audience. A cold prospect's mailbox does none of this. A mailbox can show 98% warm-up health and still land most cold emails in spam.

What stays honest:

- **Initial spam share**: the share of warm-up emails that landed in spam before a peer rescued them. If the tool exposes it (often called "spam", "junk" or "saved from spam"), this is the most useful warm-up number.
- **Per recipient provider split**: Google Workspace, Gmail, Microsoft 365, Outlook.com and others filter differently. An average hides a provider that is failing.
- **Trend over time** for the same mailbox, more than the absolute level.

## Step 1. Collect the data

Ask for, per mailbox or per domain:

1. Warm-up age (days since warm-up started) and current daily warm-up volume.
2. Headline score or health.
3. Emails landed in spam or saved from spam, over the last 7 and 30 days.
4. The same numbers split by recipient provider, if available.
5. Whether the mailbox already sends cold email, and how many per day.

## Step 2. Check readiness

- New mailboxes warm up for at least 2 weeks before any cold sending. Ramp cold volume gradually after that.
- Keep warm-up running at a low volume while the mailbox sends cold email.
- A mailbox younger than 14 days is "keep warming" regardless of its score.

## Step 3. Look for red flags

Flag each as `ACT` or `WATCH`:

1. `ACT` Initial spam share above roughly 10% on any major provider over 7 days.
2. `ACT` Spam share rising week over week on the same mailbox.
3. `ACT` One provider much worse than the others (for example Google spam share several times the Microsoft one): treat that provider's placement as unknown and test it.
4. `ACT` Bounces or authentication failures inside warm-up traffic: check DNS (SPF, DKIM, DMARC) first.
5. `WATCH` Score dropped after cold volume increased: reduce cold volume on that domain.
6. `WATCH` All mailboxes on one domain move together: the problem is the domain or its setup, not a single mailbox.

## Step 4. Decide how to measure real placement

Warm-up data can rank mailboxes against each other; it cannot give the cold inbox rate. For that, recommend a seed placement test:

- Send the real cold copy to a seed list that covers Google and Microsoft recipients.
- Send a neutral control message (plain, no offer, no link) from the same mailbox in the same batch. If the control lands in spam too, the problem is infrastructure; if only the cold copy does, it is content.
- Read results per recipient provider.

## Output format

1. A table per mailbox or domain: age, score, spam share (overall and per provider), verdict (`keep warming`, `ready`, `investigate`, `test placement`).
2. Red flags with the numbers that triggered them.
3. The next action in one line each.

## Rules

- Never convert a warm-up score into an inbox rate.
- Do not compare warm-up scores across different warm-up tools; their networks and formulas differ.
- Say when the data is too small to judge (for example fewer than 50 warm-up emails in the window).

## Example

Input: "12 mailboxes on 3 domains, 21 days of warm-up, all show 97-99% health. One domain shows 18% saved from spam on Gmail, the others under 3%. Can we start cold?"

Output (abridged):

| Domain | Age | Health | Spam share (Gmail) | Verdict |
|---|---|---|---|---|
| example-mail.com | 21 d | 98% | 2% | ready, ramp slowly |
| example-team.com | 21 d | 97% | 18% | investigate, test placement |

Red flag: example-team.com lands 18% of warm-up in Gmail spam despite 97% health. Check DNS, keep it off cold sending, run a seed test with a neutral control.

Download SKILL.md · Download ZIP

FAQ

Questions

Does a 100% warm-up score mean my cold emails land in the inbox?

No. Warm-up peers open, reply and move emails out of spam, so the score describes a friendly audience. Cold prospects do none of that. Use a seed placement test to measure cold inbox rate.

How long should I warm up a new mailbox?

At least 2 weeks before sending cold email, then ramp cold volume gradually. Keep warm-up running at a low volume after you start sending.

Which warm-up number should I watch?

The share of warm-up emails that first landed in spam, split by recipient provider, and its trend week over week. The headline score changes too little to warn you early.

What should I check first if warm-up emails land in spam?

Authentication. Run the free SPF, DKIM and DMARC checker on the sending domain, then look at volume and content.

Mailboxes, warm-up and sending in one place

$2.50 a mailbox a month. DNS records are set for you, and every mailbox shows its warm-up numbers from day one.